Anything that you introduce into you body, will affect your body in one way or another. An alcoholic will not get a disease, neither bacterial nor viral, from being an alcoholic.
However, your resistance tends to become less and less able to fend off disease. Alcoholics tend to drink instead of eat. The body is forced to feed off itself. The more you drink & use - the longer you drink & use - the more damage you do to your body, it's organ's, and it's ability to stay healthy. Also, alcoholics tend to make decisions that put themselves into less than safe situations.
So, ultimattely, by nature of the disease, alcoholism does become a gateway for opertunistic viral & bacterial infections.
Only problem is, alcoholics get sober when they hit their own personal bottom - which isn't necessarily when their body may need it to survive. Many don't make it - their unspoken choices become jails, institutions, and death.
My own sobriety - more than 21 years of a clean and sober life!